|Publication number||US7584047 B2|
|Application number||US 10/869,413|
|Publication date||Sep 1, 2009|
|Filing date||Jun 16, 2004|
|Priority date||Jun 17, 2003|
|Also published as||US20040267452|
|Publication number||10869413, 869413, US 7584047 B2, US 7584047B2, US-B2-7584047, US7584047 B2, US7584047B2|
|Inventors||Yohji Igarashi, Masaaki Sugano, Takayuki Watanabe|
|Original Assignee||Alpine Electronics, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Non-Patent Citations (1), Referenced by (4), Classifications (17), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to methods and apparatuses for detecting objects around vehicles, and more specifically, to a method and apparatus that are capable of accurately detecting an obstruction on a road.
2. Description of the Related Art
A radar device mounted in a vehicle, such as a millimeter-wave radar device, may be used to detect a preceding vehicle. This function may be utilized for speed control using an accelerator or a break to keep a space between vehicles in fields of an anti-lock brake system (ABS) and cruise-control techniques, and also used for steering control. Locations where such a radar device is utilized include straight roads such as freeways, on which vehicles can travel at high speed. Such radar devices are designed so that its receiving sensitivity can detect vehicles traveling ahead in the same direction and oncoming in the opposite direction and obstacles at sides of roads, such as guardrails, and signs.
Japanese Unexamined Patent Application Publication No. 10-221451 discloses a manner of determining whether an object ,such as a preceding vehicle or a roadside structure, detected by a vehicle-mounted radar device is an obstruction. Specifically, a relative location of an object with reference to a vehicle is calculated on the basis of signals supplied by a vehicle-mounted radar device, an absolute location of the object based on the relative location and a current position of the vehicle is found, the absolute location is compared to location data on a roadside structure, and thereby the object is thereby determined to be or not be a roadside structure.
The vehicle-mounted radar devices, such as millimeter-wave radar have a fixed receiving sensitivity. Therefore, when the receiving sensitivity is set at a rather high level (a threshold of strength of received radio waves for detecting an object is set at a rather low level), as illustrated in
However, detecting conditions vary with surroundings; for example, as shown in
The device of Japanese Unexamined Patent Application No. 10-221451 requires distinguishing whether a detected object is a scanning target (another vehicle) or an object not to be scanned (a roadside structure), and it is necessary to compare an absolute location with location data on the roadside structure. This comparison operation places a heavy load on the radar device, resulting in a problem in which obstructions traveling at high speed cannot be detected.
Accordingly, it is an object of the present invention to detect a target (e.g. another vehicle) accurately even when detecting conditions vary with surroundings, such as tunnels, bridges, and sound barriers.
Another object of the present invention is to detect a scanning target without distinguishing between a scanning target (e.g. another vehicle) and an object not to be scanned (a roadside structure).
A further object of the present invention is to detect a scanning target on the basis of comparison of distances.
According to a first aspect, geographical data is referred to; it is monitored whether a vehicle reaches a point to change a sensitivity of detecting an object of a radar device; the sensitivity is changed when the vehicle reaches the point to change the sensitivity; it is monitored whether the vehicle reaches a point to reset the sensitivity; the sensitivity is reset to its original level when the vehicle reaches the point to reset the sensitivity. Therefore, a target can be accurately detected, even when detecting conditions vary with surroundings, such as a tunnel, or a bridge.
According to a second aspect of the present invention, three-dimensional (3-D) geographical data is referred to; a distance DA between a position of a vehicle and a detecting target in the range of 360 degrees; and an area for the detecting target is defined by the distance DA; a distance DB to an object is measured in the range of 360 degrees; it is determined that the object (e.g. another vehicle) is present on a road around the vehicle when a location corresponding to the distance DB lies in the area for the detecting target, i.e., DB<DA; and the determination result is outputted. Therefore, a scanning target can be detected without distinguishing between a scanning target (e.g. another vehicle) and an object not to be scanned (a roadside structure), and the scanning target can be detected only by comparison of distances.
Additionally, since scanning is performed on solely an area where another vehicle can be present, unnecessary scanning operations are eliminated (effective scanning is achieved).
A vehicle positioning device 51 measures a position of the vehicle by means of, for example, a global positioning system (GPS). A geographical database 52 contains geographical data including information about identifiable points to decrease a sensitivity and reset it on individual roads, in addition to general geographical information. The vehicle positioning device 51 and the geographical database 52 may support a navigation system.
An obstruction detecting and controlling device 53 controls a radar device 56, acquires a distance and a direction to an obstruction, generates data for controlling display and/or audio message data, displays the data on a monitor 54 and/or raises an audio alarm by inputting the data to an alarm device 55. The obstruction detecting and controlling device 53 controls a sensitivity of the radar device 56 following a flowchart shown in
The radar device 56 emits a radio beam according to instructions from the obstruction detecting and controlling device 53, scans in a direction of the beam over a range of −θ to +θ, receives radio waves reflected from an object, detects a distance to the object and speed thereof in the range of −θ to +θ, and inputs the detected results to the obstruction detecting and controlling device 53.
The radar device 56 may use, for example, a vehicle-mounted millimeter-wave radar module under a frequency modulated continuous wave (FMCW) system. The radar device 56 has: a radar controller 61 including a driving circuit 61 a and a signal processing unit 61 b; a transmitting and receiving circuit 62 including a radio beam emitting unit 62 a for emitting a radio beam in response to a driving signal from the driving circuit 61 a and a reflected radio-wave receiving unit 62 b for receiving the radio waves reflected from the object; and a beam-scanning antenna 63 for beam-scanning over the range of −θ to +θ. The signal processing unit 61 b switches between threshold levels of strength of radio waves for detecting an object in accordance with a sensitivity indicated by the obstruction detecting and controlling device 53. On the basis of reflected radio-wave signals greater than or equal to the threshold, it then computes a distance and a direction to the object, and speed thereof, and inputs the results to the obstruction detecting and controlling device 53.
The obstruction detecting and controlling device 53 acquires a position of the vehicle from the vehicle positioning device 51 (act 101), refers to geographical data, and determines whether the vehicle has reached a point to decrease a radar sensitivity (act 102). If not, processing repeats acts 101 and 102. If the vehicle has reached the point, the obstruction detecting and controlling device 53 provides the radar device 56 with instructions SCD for decreasing the sensitivity (act 103). The radar device 56 thus sets a threshold of strength of reflected radio waves for detecting an object at a higher level, thus the sensitivity is set at a rather low level.
The obstruction detecting and controlling device 53 acquires a position of the vehicle from the vehicle positioning device 51 while detecting an object under the low-level sensitivity (act 104), refers to the geographical data, and determines whether the vehicle has reached a point to reset the radar sensitivity to its original level (act 105). If not, the processing repeats acts 104 and 105. If the vehicle has reached the point, the obstruction detecting and controlling device 53 provides the radar device 56 with instructions for resetting the sensitivity to its original level (act 106). The radar device 56 thus sets the threshold of strength of reflected radio waves for detecting an object at a lower level, thus the sensitivity is set at a rather high level, and detecting objects continues under the reset sensitivity.
An obstruction detecting and controlling device (not shown) of a vehicle CAR refers to 3-D geographical data and calculates a distance DA from a position of the vehicle CAR to a detecting target (a roadside building) BLD in the range of 360 degrees (see
According to a first aspect, a scanning target can be detected without distinguishing between a scanning target OBL (e.g. another vehicle) and an object not to be scanned BLD (a roadside structure), and the scanning target can be detected solely by comparison of distances.
The obstruction detecting and controlling device 53 refers to 3-D geographical data and calculates a distance between a position of the vehicle and a roadside building in the range of 360 degrees, thereby defining an area for a detecting target before radar scanning (act 201).
With respect to a direction in which the object greater than or equal to the reference height h0 is present, it is determined that an object not to be scanned (e.g. building) is present in the direction; a distance DA to the object is recorded associated with its direction (act 201 d). On the other hand, with respect to a direction in which the object greater than or equal to the reference height h0 is not present, an effective distance of the radar device is recorded as a distance DA associated with its direction (act 201 e). In view of sidewalks, a distance DA is recorded after the width of a sidewalk is subtracted from it.
Then, it is determined whether a distance DA has been measured in all directions (act 201 f); if not, a set direction is rotated a predetermined angle (act 201 g) and processing of act 201 c and subsequent acts is repeated.
According to the processing of defining the area for the detecting target, when buildings greater than or equal to the reference height h0 are present, which are hatched in
Referring back to
Then, the obstruction detecting and controlling device 53 provides instructions for scanning (act 203), acquires a measured distance DB to an object in a scanning direction by the radar device 56 (act 204), and compares the distance DA to a roadside building in the scanning direction with the measured distance DB (act 205).
If DA>DB, the object is an obstruction, such as another vehicle, present on the road; the obstruction detecting and controlling device 53 displays it on the monitor 54. If the obstruction is too close, the alarm device 55 raises an audio alarm (act 206). Alternatively, the speed of the vehicle may be automatically reduced in accordance with a distance to the obstruction (another vehicle).
Then, it is determined whether scanning is completed in all directions (act 207); if not, the processing goes back to act 203, performs scanning in the next scanning direction, and repeats subsequent steps.
The 3-D geographical data may be installed in a vehicle-mounted device in advance, or only necessary sections may be provided externally via communications.
It is to be understood that a wide range of changes and modifications to the embodiments described above will be apparent to those skilled in the art and are contemplated. It is therefore intended that the foregoing detailed description be regarded as illustrative, rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of the invention.
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|U.S. Classification||701/436, 180/167|
|International Classification||G06F21/00, G01V3/12, B60R21/00, G01S13/86, G01S7/40, G01S5/14, G01S13/34, G01S7/22, G01S13/93|
|Cooperative Classification||G01S13/931, G01S7/4021, G01S13/86, G01S19/14, G01S7/22, G01S13/34|
|Sep 7, 2004||AS||Assignment|
Owner name: ALPINE ELECTRONICS, INC., JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:IGARASHI, YOHJI;SUGANO, MASAAKI;WATANABE, TAKAYUKI;REEL/FRAME:015764/0260;SIGNING DATES FROM 20040819 TO 20040823
|Sep 14, 2010||CC||Certificate of correction|
|Feb 22, 2013||FPAY||Fee payment|
Year of fee payment: 4